FLASH Irradiation with Proton Beams: Beam Characteristics and Their Implications for Beam Diagnostics

Abstract

FLASH irradiations use dose-rates orders of magnitude higher than commonly used in patient treatments. Such irradiations have shown interesting normal tissue sparing in cell and animal experiments, and, as such, their potential application to clinical practice is being investigated. Clinical accelerators used in proton therapy facilities can potentially provide FLASH beams; therefore, the topic is of high interest in this field. However, a clear FLASH effect has so far been observed in presence of high dose rates (>40 Gy/s), high delivered dose (tens of Gy), and very short irradiation times (<300 ms). Fulfilling these requirements poses a serious challenge to the beam diagnostics system of clinical facilities. We will review the status and proposed solutions, from the point of view of the beam definitions for FLASH and their implications for beam diagnostics. We will devote particular attention to the topics of beam monitoring and control, as well as absolute dose measurements, since finding viable solutions in these two aspects will be of utmost importance to guarantee that the technique can be adopted quickly and safely in clinical practice.

Future Developments in Charged Particle Therapy: Improving Beam Delivery for Efficiency and Efficacy

“…( 42 ). Alongside this is also the need for better instrumentation systems which can operate proficiently under FLASH conditions ( 168 ). A fundamental challenge is achieving the requisite FLASH beam parameters for PBS delivery with clinical accelerator systems, given safety restrictions ( 169 ).…”

“…The necessary accelerator and beam delivery developments required to deliver FLASH with clinical protons are detailed extensively by Jolly et al (42). Alongside this is also the need for better instrumentation systems which can operate proficiently under FLASH conditions (168). A fundamental challenge is achieving the requisite FLASH beam parameters for PBS delivery with clinical accelerator systems, given safety restrictions (169).…”

Repurposing Proton Beam Therapy through Novel Insights into Tumour Radioresistance

“…FLASH radiotherapy can be delivered using low energy electrons, but tissue penetration is low, limiting its use to more superficially located tumours. Higher energy PBT enables greater tissue penetration and irradiation of deep-seated tumours and PBT facilities based on cyclotrons and synchro-cyclotrons have already shown the ability to reach FLASH dose rates in several experiments [77,78]. Conceptually, there are two forms of FLASH PBT that are currently being studied.…”

“…However, the unique dosimetric profile and dose-sparing effects of protons are not fully exploited. Therefore, there is greater interest in developing Bragg peak FLASH, which combines the dose-sparing effects of the Bragg peak with ultra-high dose rate delivery [78,79].…”

A new emittance selection system to maximize beam transmission for low‐energy beams in cyclotron‐based proton therapy facilities with gantry

“…As such, PBS irradiation with high‐intensity beams will reduce beam‐on time and thus shorten total delivery times, making motion mitigation techniques such as breath‐hold or gating more efficient and patient‐friendly. Additionally, higher beam intensities will permit efficient delivery of hypo‐fractionated treatments and will be an important enabler of proton FLASH techniques 17–19 …”